A memory device having a three-dimensional structure has been proposed in which memory holes are made in a stacked body in which insulating layers are multiply stacked alternately with conductive layers that function as control gates of memory cells, and silicon bodies used to form channels are provided on the side walls of the memory holes with a charge storage film interposed between the silicon bodies and the side walls.
As the conductive layer, a silicon layer doped with an impurity has been proposed; and it has also been proposed to perform metal siliciding of a portion of the silicon layer to reduce the resistance of the conductive layer. A conductive layer of a metal layer also has been proposed.
Also, as a structure to respectively connect the multiple conductive layers that are stacked to other interconnect layers, technology has been proposed in which the multiple conductive layers are patterned into a stairstep configuration, and multiple contact holes having different depths that reach the conductive layers of each level are made simultaneously. In the simultaneous patterning of the multiple contact holes having the different depths, a difficult control is necessary to stop the etching at the conductive layer of each level.